1. Field of the Invention
This invention relates to a biometric authentication method and a biometric authentication apparatus, which utilize biometrics characteristics which are a portion of a human body, to authorize individuals, and in particular relates to a biometric authentication method and a biometric authentication apparatus which are suitable for improving the speed of verification of numerous registered biometrics characteristic information sets against detected biometrics characteristic information.
2. Description of the Related Art
There are numerous portions of the human body which can be used to differentiate the individual, such as fingerprints and toeprints, the retinas of the eyes, facial features, and blood vessels. With advances in biometrics technology in recent years, various devices have been provided which identify biometrics features of a portion of the human body to authenticate individuals.
For example, comparatively large amounts of individual characteristic data are obtained from blood vessels in the fingers and palms of the hands, and from palmprints. Blood vessel (vein) patterns remain unchanged throughout life from infancy and are regarded as being completely unique, and so are well-suited to individual authentication.
In order to utilize this biometrics information to perform individual authentication, at the time of registration or of authentication the user brings his palm into proximity with an image capture device. The image capture device emits near-infrared rays, which are incident on the palm of the hand. The image capture device uses a sensor to capture near-infrared rays reflected from the palm of the hand. Hemoglobin in the red corpuscles flowing in the veins has lost oxygen. This hemoglobin (reduced hemoglobin) absorbs near-infrared rays at wavelengths near 760 nanometers. Consequently when near-infrared rays are made incident on the palm of a hand, reflection is reduced only in the areas in which there are veins, and the intensity of the reflected near-infrared rays can be used to identify the positions of veins (blood vessel images).
The user first uses an image capture device to register vein image data of the palm of his own hand in a server or on a card. Then, in order to perform individual authentication, the user employs an image capture device to cause the vein image data of his own hand to be read. The registered vein image is verified against the vein pattern of the vein image for verification thus read, and individual authentication is performed (see for example Japanese Patent Laid-open No. 2004-062826 (FIG. 2 through FIG. 9)).
In such a biometric authentication system for example in the field of fingerprint authentication, a method has been disclosed in which characteristic data A at a comparatively low level (at which outside leakage is tolerated), and characteristic data B at a comparatively high level which is to be kept confidential, are stored in an IC card. The characteristic data A is transmitted from the IC card to an external device comprising a fingerprint sensor, and the external device performs verification of the characteristic data A (called primary verification), and transmits the verification result and characteristic data B′ extracted from the image from the fingerprint sensor to the IC card; within the IC card, verification with the characteristic data B is performed (called secondary verification) (see for example Japanese Patent Laid-open No. 2000-293643 (FIG. 5 and FIG. 6)).
However, with progress in biometric authentication technology in recent years, a large amount of biometrics characteristic data has been registered. For example, a large number of biometrics characteristic data sets are registered on servers for use by security systems which manage ingress and egress in apartment buildings, office buildings and other facilities.
In such a mode of use, numerous verifications of captured biometrics information against registered biometrics information must be performed, so that time is required for verification. Particularly when precision is required in biometrics verification, the large quantity of biometrics characteristic data and the complexity of the verification algorithms used means that even more time is required for verification. As a result the wait time for users is lengthened, which in turn impedes adoption of the technology.
Methods are conceivable in which users are assigned IDs, the IDs are registered together with biometrics characteristic data, and the user also inputs his ID; however, the assigning of separate IDs to each user is troublesome, and may result in inconvenience to the user. For example, in the case of application to ingress and egress to and from a facility, it is more convenient to a user who enters and leaves the facility to be able to use an ID assigned to the facility to perform biometric authentication. In this case also, verification of captured biometrics information against biometrics information registered for the ID must be executed numerous times, so that time is required for verification.
And, in biometric authentication based on the above-described primary verification and secondary verification, the characteristic data A at the comparatively low level (at which outside leakage is tolerated) is specific to that user, and when applied to this mode of use also, the effect in shortening verification time is minimal.